1. Field of the Invention
This invention relates generally to water pressure regulating devices, and more particularly to systems for dampening water pressure fluctuations in pump systems used to supply fluids to wafer cleaning stations.
2. Description of the Related Art
As is well known, semiconductor devices are fabricated from semiconductor wafers, which are subjected to numerous processing operations. These operations include, for example, impurity implants, gate oxide generation, inter-metal oxide depositions, metallization depositions, photolithography pattering, chemical mechanical polishing (CMP), etc. Although these processes are performed in ultra clean environments, the very nature of many of the process operations is to blame for the generation of surface particles. For instance, when CMP operations are performed, a film of particles and/or metal contaminants are commonly left behind.
Because surface particles can detrimentally impact the performance of an integrated circuit device, wafer cleaning operations have become a standard procedural requirement after certain process steps. Although cleaning operations are rather procedural, the equipment and chemicals implemented to perform the actual cleaning are highly specialized. This specialization is important because each wafer, being at different stages of fabrication, represents a significant investment in terms of raw materials, equipment fabrication time, and associated research and development.
To perform the cleaning operations in an automated manner, fabrication labs typically employ a cleaning system. A typical cleaning system may be, for example, a Synergy.TM. cleaning system from OnTrak.TM., of Fremont, Calif., which is a subsidiary of Lam Research Corporation, also of Fremont, Calif. A typical Synergy.TM. cleaning system employs two brush stations, where each brush station has a set of brushes for cleaning the top and bottom surfaces of a wafer. Each of the brushes are commonly configured to deliver chemicals and DI water Through-The-Brush, to enhance the cleaning ability of the system. The system typically also includes a spin-rinse station, where a wafer, after being cleaned in the brush stations is rinsed with DI water and dried before completing the cleaning cycle.
As can be appreciated, it is very important that facility lines, which supply the DI water to the cleaning system supply the water at substantially steady water pressure levels. Unfortunately, the facility lines in different fabrication labs vary substantially. In some cases, the pressure levels are too high and in others too low. In those cases where the pressure level is too low, laboratory technicians sometimes connect a water pump between the facility lines supplying the DI water and the cleaning system. Although water pumps are able to increase pressure levels, a downside to water pumps is that large pressure fluctuations are also introduced and passed to the cleaning system. In view of the fact that cleaning systems are designed to carefully apply selected amounts of DI water to produce very specific chemical solutions, (i.e., mixture) pressure fluctuations can cause erratic changes in the concentration of applied solutions.
In view of the foregoing, there is a need for pump systems and methods for implementing booster pump systems that minimize the degree of water pressure fluctuations communicated to wafer cleaning systems.